Propeller



. 1,460,230 L. DE MONGE June 26, 1923.

PROPELLEH F iled Oct. 27

lNl/ENTOF Laws 0 No E flTTOP/VFKS B awwf Fatentcd June 2%, $23.

atria LOUIS Du MONGE, F PARI$, FRANCE.

PBOPELLEB.

Application filed Gctober 27, 1920. Serial No. eaaooe.

' dated November 8, 1917), of which the following is a specification.

This invention relates to aircraft propellers constructed of wood, and has for its object a particular outline for this class of propellers whereby the efficiency of the same shall be increased; This advantageous-result is partly due to the tapered form which,

is given to the ends of the propeller blades in such cases. 7 v

The accompanying drawing represents the outline of a propeller according to this invention,

Figs. 1 and 2 show a propeller blade respectively in front view and in side view. In Fig. 2 are represented the cross-sections of the blade at various points along the same.

The propeller is drawn by taking as the axis of the outline of each blade a. straight line a b which is perpendicular to the axis of rotation m w and is situated at a short distance 0 a from this axis, being forwardly located with reference to the sense of rotation. The projection of the outline of the propeller upon a plane perpendicular to the axis of rotation (Fig. 1) is then drawn in the following manner: Having chosen the length of the propeller 0 I), this is divided into three equal parts; at the point 9 which is located at the outer third portion is drawn a perpendicular upon which is marked off the maximum width 6' f to be given to the said projection of the outline, placing onethird of this width forwardly at e' and two thirds rearwardly at f. The two outer thirds of the blade are to have substantially the shape of a willow leaf. The outline is drawn for instance by the use of a quarter of an ellipse at the forward part having 9 b and g e as axes, and a quarter of an ellipse at the rear part having g b and g f as axes. It is to be noted that in all the section parallel to e f, the axis 0 6 passes through the anterior third of the segments located between the arcs b e and L f. mainder of the outline of the blade, this is drawn by the use of the curves e k and f i which have a tangent connection with the As to the rearcs b e and b f on the one hand, and are connected with the circumference of the hub on the other hand, these curves proceeding gradually towards each other up to a short distance from the hub.

As to the crosssections of the-blade (Fig. 2) their shapes and directions are chosen and laid out in the usual manner. The direction is laid out, according to the rules for $5 drawing helical surfaces, by means of a series of straight lines proceeding from a point 3 of a perpendicular axis and passing through the section points 9 g 9 etc, According to the present invention, of each cross-section is determined both by the direction thus found and by the outline it e I) f 2' produced as above specified. The position of each section is defined by the fact that the axis 0 6 passes through the middle of the thickness 0 d of the blade and also through the forward third of the width thereof e f.

These conditions of outline will afford a blade having a very considerable resistance to fiexion and tension stresses produced during the rotation, and chiefly from the fact that the centers of gravity of the cross-see tions are situated exactly or very approximately upon a straight line. On the other 35 hand, as regards the propulsive efliciency of the propeller, it is shown -by experience that the above-described shape has a considerable advantage, this being explained by the fact that near the end of the blade, linear speed of rotation is greatest, the active surface has a width which decreases in a very continuous manner between the edges of the curves, thus possessing not only the advantage of sharpness of blade whereby the prejudicial whirling edects are reduced, but also the advantages of a relatively large surface such as is necessary to secure a high propulsive action.

It should be understood that the configuration of the part of the blade adjacent the hub is of much less importance than that of the outer lying portion, by reason of the smaller linear speed rotation. The shape of this internal part as here shown is while preferable not essential as in the case of the external part, especially beyond the maximum section 6' f.

Claims:

1. An aircraft propeller whose configura tion is determined by the fact that the point situated upon each ross-section of the blades the length 70 at which the 90 at the anterior third partof the length f) and at the middle part of the width (0 d) of the cross-section is located upon a straight line (a 6) common to all the cross-sections of a given blade, the said straight line being situated in a plane perpendicular to the axis of rotation of the propeller and at a short distance therefrom.

2. An aircraft propeller whose configura tion is determined by the fact that the point situated upon each cross-section of the blades at the anterior third part of the length (e f) and at the middle part of the width (0 d)' of the cross-section is located upon a straight line (a 6) common to all the cross-sections of a given blade, the said straight line being situated in a plane perpendicular to the axis of rotation of the propeller and at a short distance therefrom, the various ems-sections having difierent lengths (e 7) whose maximum is situated at two-thirds of the length of the blade outwardly of the axis of rotation and which then decrease on one side towards the point of the blade and on the opposite side to within a short distance from the hub of the propeller.

In testimony that I claim the foregoing as my invention I have signed my name in presence of two subscribing witnesses.

LOUIS DE MONGE.

Witnesses! CLEMENT S. EDWARDS, MAURICE RAUX. 

